| 摘要 |
<p>1446026 Porous-coated particles MITSUBISHI PETROCHEMICAL CO Ltd and FUJIMI KENMAZAI KOGYO KK 8 Aug 1973 [10 Aug 1972] 37610/73 Headings B1E and B2E [Also in Division C1] A particle comprises a core of metal or metal oxide catalyst having a coating or a sheath which is formed with pores to allow the passage of fluid through the coating or sheath, the coating or sheath having greater crush strength and abrasion resistance than the core. A space may be formed between the sheath and core. In a preferred method, catalyst core material is mixed with water to form a paste which is granulated. The granules are then coated with a paste of sheath material and the particles are then dried and sintered. Sintering is omitted when coatings of powdered organic particles are used. The sheath material may be particulate or be formed of particles and a fusable binder. The material of the sheath may include or comprise the same material as the core. The core material may be an oxidation catalyst such as MnO 2 or catalysts such as Pt or Pd supported on an inert carrier. The space between the sheath and core may be formed by providing an intermediate coating of a material which is combustible during sintering, such materials being e.g. walnut husk powder or fibres, sawdust cellulose, polyolefins, polystyrene, wheat flour, microcrystalline cellulose, cornstarch, saccharide or polyvinyl alcohol. It is also possible to use materials which are soluble in water, acid or alkali, or a sublimatable material (e.g. camphor) to make the space. The space forming material can be used in forming the pores in the sheath or in the core. The sheath material may. be ceramic powder (e.g. fused Al 2 O 3 , SiC, Al 2 O 3 , SiO 2 , or zircon), glass powder (e.g. sodium, lead or borosilicate glass), metal powder (e.g. Fe, Al, Cu, Sn, Pb or Zn), alloy powder (e.g. gun metal, stainless steel), MgO, cements (e.g. Portland or alumina cement), or organic polymers. When the sheath material is difficult to bond by sintering a binder such as clay, kaolin, feldspar or glass powder is used. An MnO 2 / Fe 2 O 3 core with a glass/alumina powder sheath is stated to catalyse oxidation CO and Hydrocarbons in exhaust gases. Examples of MnO 3 with various sheaths are given wherein phenol is converted to 2, 6 xylenol and o-cresol.</p> |
